Apax, which can draw on co-investors such as Chinese and Singaporean sovereign wealth funds for financing, has beaten other rivals to clinch the deal. Goldman Sachs Capital Partners and Sweden's EQT put ISS up for sale in the summer with a dual-track IPO process and several private equity firms vying to buy it.

ISS's core business is cleaning and the company has units in 50 countries, employing more than 520,000 staff. It also operates globally in catering, security, property services and call centres. In 2009, the company had £7.8bn of sales, with earnings of £550m projected to jump to £620m next year.

Bids from CVC working with Apollo, and Bain Capital's consortium with Nordic Capital, CD&R and Blackstone have been rejected.

Goldman, which is also advising on the sale, selected Apax for the deal, giving it less than two months to put in place the funds needed.

The private equity firm will do the deal alongside GIC, the Singaporean sovereign wealth fund, and a small number of other financial backers.